Apparatus for the manufacture of explosives



July 20, 1948. A. o. FRANZ ET AL APPARATUS FOR THE MANUFACTURE OFEXPLOSIVES Filed March '51, 1943 [HI lllllllllll ll llllillllllllill IINVENTOR AP VEL 0. FEANZ 3 OE/NCAEPt/NGEE BY am a. w

ATTORNEY Patented July 20, 1948 APPARATUS FOR THE MANUFACTURE OFEXPLOSEVES Arvel 0. Franz and Orin C. Keplinger, Alton, Ill.,

assignors to Olin Indu of Delaware stries, Inc., a corporationApplication March 31, 1943, Serial No. 481,369

6 Claims. 1

This invention relates to the manufacture of explosives and moreparticularly to a continuous nitration apparatus for use in themanufacture of explosives, The nitration process set forth herein isdescribed and claimed in our co-pending application, Serial No. 481,368,filed March 31, 1943, issued as U. S. Patent 2,415,423.

Heretofore explosives have been manufactured in both intermittenttypeand continuous type nitration apparatus. Such intermittent apparatushas the serious disadvantage of being relatively large and expensivewith a relatively large amount of explosive in process. Prior continuousapparatus are attended by the disadvantage that overnitration andoxidation of the materials to be nitrated at times occurs, with aresultant decrease in efiiciency of production and a lowering of qualityof the product. Such overnitration or oxidation is usually the result offailure to maintain each portion of the material to be nitrated incontact with its proper portion of nitrating acid until the reaction iscompleted, or failure to maintain the reaction mixture at the propertemperature. With certain of the prior nitration apparatus thedisadvantage is also obtained that the reaction mixture is recirculatedin the reaction vessel so that the nitrated product is continuallybrought into contact with fresh nitrating acid.

It is therefore an object of this invention to provide a continuousapparatus for the manufacture of such explosives free of thedisadvantages attending such prior apparatus.

Another object of the invention is to provide an improved continuousnitration apparatus for manufacturing polynitrated explosives.

A further object of this invention is to provide an improved apparatusfor continuous nitration in which oxidation and overnitration areprevented.

A still further object of the invention is to provide a continuousapparatus for effecting aneflicient nitration in the manufacture ofpolynitrated explosives in which the temperature is readily controlledat the desired level.

Other objects and advantages will become apparent from the followingdescription and drawing in which,

Figure 1 shows a plan view of a nitrating apparatus illustrating oneembodiment of this invention, and

Figure 2 is a vertical section, taken at XX", of

the nitrating apparatus of Figure 1, and I Figure 3 is a sectional viewtaken along lin 3-3 of Figure 2, and

Figure 4 is a sectional view taken along line 44 of Figure 2.

These objects and advantages are obtained in accordance with the presentinvention by the provision of a novel apparatus in which the nitratingacid and the material to be nitrated are uninterruptedly broughttogether, uniformly mixed, and the resulting mixture is progressivelypassed along an extended path through successive zones of forcedcirculation so controlled as to impede the direct flow of fresh materialfrom the point of entrance to the point of exit and concurrentlyminimize the possibility of back-flow of treated material from near thepoint of exit to the point of entrance. During thepassage through saidpath the mixture is maintained at reaction temperature and subjected toa plurality of zones of opposing forced circulation, the spent acid andnitrated materials being continuously discharged at the end of saidpath.

In the manufacture of such polynitrated explosives as tetryl, thenitration reaction is not instantaneous but requires a period of timefor completion. In the manufacture of such polynitrated explosives asnitroglycerine, no extended period of time is required for the nitrationreaction, but a great quantity of heat is developed during the reactionwhich must be dissipated in order to prevent the mixture fromoverheating. The apparatus of the present invention is suitable forcarrying out both types of reactions.

It has now been found that the heat can be adequately dissipated and theperiod necessary for reaction is readily obtained when the nitratingmixture is passed through a vertical U-shaped vessel provided withagitators which form the mixture into a plurality of zones of opposingcirculation in accordance with this invention.

Referring to the drawing, which represents a preferred embodiment of theapparatus forearrying out the nitration reaction, the tubular vessel isin the form of an upright U-tube I. The U-tube is provided with externalcooling or heating jackets 2, 3, 4, 5, 6, 1, and 8 having inlets andoutlets 25. Charging inlets 9 and ID are provided for introducing thenitrating acid and material to be nitrated into the entrance leg ll ofU-tube I. An outlet 12 is provided on the exit leg 13 of U- tube fordischarging the spent acid and product. The inlets 9 and ID forintroducing the reagents into the nitrator are preferably maintained atsome distance above the surface of the reaction mixture in the nitrator.By thus maintaining the inlets out of contact with" the reaction mixtureall possibility for either the reaction mixture or any of itsconstituents to return through either inlet 9 or III is avoided. This isa distinct advantage over certain of the prior apparatus in which it waspossible for the reaction mixture to back up into the feed line for thenitrating acid or the feed line for the material to be nitrated andthus'create a hazardous condition.

A plurality of agitators, for instance l4, l5, I6,

20, 2 I, and 22, maintain the mixture uniform andmaintain anyundissolved material uniformly distributed throughout the mixture. Theagitators may be so adjusted that no appreciable head of I liquid occursin either arm II or l3 and are so shaped and arranged th'at they formthe mixture into at least two zones of opposing circulation so thatpractically no part of the mixture in arm I3 returns to arm H.

An outlet I8 is provided at the bottom'of vessel I so that the nitratorcan be completely drained in case of emergency, or for cleanin purposesand the like. In operation the reagents are fed in proper proportionthrough inlets -9 and ill in the arm H to form an initial reaction zonewith thorough mixing by the agitator I4, and during the initialreaction, the mixture is cooled to the desired temperature by heatexchange with the cooling medium circulated. through the jacket 2.Thermometer wells such as are illustratedat 26 may be employed todetermine the temperature of the mixture in the vessel. The mixture thenpasses through thesucceeding zones of localized agitation, thetemperaturebeing controlled by meansof jackets, for instance 3, 4, 5, 6,1, and 8, and the product and spent acid are discharged by overflowingfrom theoutlet l2 at a rate corresponding to the feed. of raw materials.Vents suchas 23 and 24 may be employed toremove fumesor for instance tomaintain the mixture at atmospheric pressure.

Propeller type, paddle type,- or any other suitable type of agitatorsmay be employed, provided they are so adjusted thatat least some of thesuccessive. agitatorsact differently on the fluid thereadjacent,respectively. For instance, when the agitator shafts l1 and i9. arerotated in a clockwise direction (as seen in Figure 1) the mixture inboth the charging and discharging arms I I and I3, respectively, tendstoswirl likewise in a clockwise direction (as viewed from above), but atthe bottom of the U, where the two columns of mixture join,the-direction of circulation of the one opposes. that of the other sothat zones of opposing circulation. are set up. Any suitable mechanismmay be employed for driving the shafts l1 and I9 in the same directionas viewed from above (1. e., opposite directions if viewed along theaxis-of the U-tube from one end). For example, each of shafts IT and!maybe provided with pinions 3! and 39, respectively, meshing with asingle drive gear38.

By feeding the raw materials into one arm of the U-shaped. vessel andcontrolling the agitation to form suchopposing zones of forcedcirculation, the rawmaterials are prevented from short circuiting fromthe inlets 9 and lllto the'outlet I2" before the-reaction has beencompleted and likewise, the completely reacted material is we ventedfromreturningto the inlet arm. so that during .thetravel of the constituentsfrom the inlets.9.and. l through the vesselto the discharge outlet. I2,each portion of thematerial to.be.nitrated. is kept uniformly mixedwith, its proper proportion of, nitrating acid.

By. way of illustration following, is atypical embodiment of theinvention describing the use of the apparatus for the manufacture oftetryl.

One part of dinitromethylaniline is dissolved in 2.43 parts by weight ofsulfuric acid (66 B.). The nitrating acid employed contains 68% nitricacid, 16% sulfuric acid, and 16% water. The diameter of the tube formingthe U-shaped vessel [employed is about 16 inches and the apparatus isabout 4 /2 feet high. The mixture travels about 1 1 feet in going fromthe inlets 9 and I9 to the outlet l2.

In firststarting the nitration the above described nitrating acid is runinto the nitrator throughinlet Illv at the rate of 18.8 gallons perhouruntil'thenitrator is about A; full. The feed of the acid-is thenstopped and the above described solution of dinitromethylaniline is runinto the-nitrator at the rate of 50 gallons per hour for an equal lengthof time. When this is accomplished the nitrator is sufiiciently filledfor the continuous nitration operation to be started. The.dinitromethylaniline solution is then fed'in through inlet 9 at a rateof about 50 gallons per hour andthenitrating acid'is simultaneously fedin. through .inlet Ill at the rate of about"l'8;8 gallons per. hour,thus providing about 0.765 part by weightof'nitric acid per eachpart byweight of'dinitromethylaniline, or only about 20% over the theoretical.acid; requirement. At this :rateof feed, i. e., a nitration cycle ofminutes', a yield of about 300 pounds of tetryl per hourwasobtained.

By increasing the rate of feed of the reagent thenitration cycle can bereduced to as short a time as 20 minutes oreven shorter. withsatisfactory results; Such increased feed of reagents provides aproportionately increased production rate. This'flexibility-ofproduction rate is of de cided advantage over prior" apparatus; I

The agitator l4 provides. for immediate and uniform mixing ofthe acid.and dinitromethylaniline; Agitatorshafts l1 and [9 are rotated in a'clockwisedirection (aszseen in Figure 1), the several. agitatorblades,in the form shown, being of the'type tendingjto' force at least thsuspended particles of adjacent non-homogeneous mixturein ahorizontalldirection. Agitators M, I6, and have their'blades so adjustedas to direct at least the suspended particles in the mixture away fromthe. side walls of the container,. as illustrated bythe arrows'39, andagitators. I5, 20, ancl2l have-their*blades'adjusted' so as to direct atleast the suspended particles in. the mixture toward the side walls, asillustrated by arrows 29. Thus within the swirling mixture of each legof'the U-tubethere are zones of locally opposing circulation wherein'atleast the suspended particles travel outwardly or inwardly in relationtothe central axlsof the tube depending upon the angle of the blades ofeach stirrer spider to the radius. Consequently at least the suspendedparticles follow a generally spiral course, of travel down one legof theU-tube and up the otherleg'to the discharge outlet, the spiral varyingin diameter and pitch depending upon the angle at which the blades areset' on' the stirrer with-theresultthat'a crossmixing effect ofcomponents is obtained while the mixture. as:a' whole continues to swirlin one direction inone leg; of the U-tube and in. the" oppositedirection (as viewed along 'the'axis'of the U-tube from oneend only).inthe other leg, of the vU-tube. The mixture is kept at. areactiontemperature. of; about 55? C. by flowing, water. or other.coolantas-required through the temperature controlling jackets 2, 3, 4,5, 6, I, and 8. The mixture in the '5 initial reaction zone has apurplish colorwhich disappears usually before reaching the bottom of theU-shaped vessel l and changes to'a yellow color which persists up to theoutlet l2.

By virtue of the vigorous agitation maintained throughout the vessel anytendency of the precipitated product to settle out is prevented. Tetrylis obtained in a yield correspondingto about 95% to 99% of theoretical,having a-pale yellow color and after moderate washing, a melting pointin the range of about 127 C. to 129 C. and an acidity calculated assulfuric acid, equal to about 0.1% to 0.3%, or even less.

Practically all over nitration and oxidation of the dinitromethylanilineis prevented by adding the proper proportion of nitrating acid,preferably not less than or not more than in excess of the theoreticalrequirement, to each part of the dinitromethylaniline and maintaining auniform mixture of materials in each zone of circulation while uniformlycontrolling the temperature of the mixture below 80 C. and preferablybetween and C. throughout the nitraton' Accordingly, the nitrationtemperature is maintained from the time of mixing of the raw materialsuntil the reaction is completed, the necessity of starting the reactionat relatively low temperatures as in customary processes and equipmentis avoided and a shorter nitration cycle is thus provided, Theprecipitation of tetryl during nitration tends to thicken the mixtureand thus materially aids in the baffling effect, resulting from thezones of opposing circulation, which prevents undesirable intermixing ofthe various strata of the mixture in the nitrator.

Following is another embodiment of the inveniton describing the use ofthe apparatus in the manufacture of nitroglycerine.

The nitrating acid employed is composed of about 50% nitric acid and 50%sulfuric acid. The nitrator has about the same dimensions as thosedescribed in the above embodiment for the nitrator used in themanufacture of tetryl. In first starting the operation, the nitrator isfilled with a spent acid containing about 20% nitric acid, 64% sulfuricacid, and 16% water. Anhydrous glycerine is then fed in through inlet 9at a rate of about 18.1 gallons per hour and the nitrating acid issimultaneously fed in through inlet If! at the rate of about 72.5gallons per hour, thus providing about 5 parts by Weight of nitratingacid per each part by weight by glycerine, with only about 28% excessover the theoretical nitric acid requirement. At this rate of feed, ayield of about 441 pounds of nitroglycerine per hour was obtained.

The mixture in the nitrator is kept at a reaction temperature of about16 C- to 20 C. by flowing any suitable refrigerant through the jackets2, 3, 4, 5, 6, 1, and 8. Any fumes that develop during the reaction arereadily disposed of through vents 23 and 24. The large amount of heatinvolved in such reactions is readily dissipated in accordance with thisinvention by means of the large cooling surface provided per unit volumeof reaction mixture and the turbulence of agitation,

Although the manufacture of tetryl and nitroglycerine are described inthe above specific embodiments, the apparatus of this invention can beused in the manufacture of other polynitrated explosive compoundspresenting similar manufacturing problems, for instance trinitrotoluene,s-cyclotrimethylenetrinitramine, tetranitroaniline, picric acid,trinitroresorcinol, pentaerythiii an U

6 ritolt'etranit'rate, the polynitrocresols, hexanitro mannite, andthelike. 1 1

In accordance with this invention the solution to be 'nitrated and thenitrating acid after being thoroughly mixed in the initial reactionzonein the nitrator tend to travel toward the discharge outlet withpractically no intermixing with subsequently added raw materials, orwith more completely reacted materials, while at the same time athorough localized circulation of the mixture is provided until thereaction is complete and the productis discharged from the nitrator. Bythus providing a'columnar mass of a circulating reaction mixture, alarge temperature exchange surface is provided perunit volume of themixture, and the temperature of the mixture can consequently be veryaccurately controlled thus greatly increasing the production efficiencyover that obtained with prior continuous apparatus.

While certain specific details are set forth herein it should beunderstood that considerable modification can be made without departingfrom the spirit and scope of the invention and that the invention is notto be limited thereby except as set forth in the appended claims.

What we claim is:

1. Continuous nitrating apparatus comprising a vessel having elongatedsubstantially vertical portions connected at the bottom, agitator shaftsin each of said substantially vertical portions, agitators carried bysaid shafts at a plurality of elevations in each of said substantiallyvertical portions, said agitators at one elevation having blades slantedsubstantially opposite tothe blades of an agitator at a differentelevation in each of said substantially vertical portions, means forcontrolling the temperature of the contents of said vessel, inlets forthe reagents at one end of said vessel and an outlet for the reactionproducts at the other end of said vessel.

2. Continuous nitration apparatus comprising a vessel formed of twoupwardly extending arms connected together at the bottom to form acontinuous substantially unrestricted passage therethrough, agitators ata plurality of elevations in each of said arms with at least one of saidagitators in at least one of said arms having its impelling surfacepitched substantially opposite to the impelling surface of an agitatorin said arm at a different elevation, inlets for the raw materials atone end of said vessel, and an outlet for discharging the reactionproducts from the other end of said vessel.

3. Continuous nitration apparatus comprising a vessel formed of twoupwardly extending arms connected together at the bottom to form acontinuous substantially unrestricted passage therethrough, agitatingmeans having agitators at a plurality of elevations in each of said armswith at least one of said agitators in one arm having its impellingsurface slanted to direct at least the suspended particles of mixturecontained in the vessel in a direction opposite that of at least oneagitator in the other arm, means for controlling the temperature of thecontents of said vessel, inlets for the reagents at one end of saidvessel, and an outlet for the reaction products at the other end of saidvessel.

4. Continuous nitration apparatus comprising a vessel formed of twoupwardly extending arms connected together at the bottom to form acontinous substantiall unrestricted passage therethrough, an agitatorshaft in each of said arms, agitators carried by said shafts at aplurality of elevations, means for rotating said agitator shafts 2inaopposite ,di-rectionssarsuviewed alongythesaxisof said vessel fromone end onlygmeansior.controh ling: the temperature: oiitha-contents:of; said ivessel;v inlets; for: thezreagentsat; oneeend: of said vessel,and: anx-outlet: for: the reaction" productsatitherothergend'oiisaidlvessel.

Apparatus ="0fr'the character describedicomprisinga tubular vessel,apluraiityofi agitator shafts 'arranged in=axial successionin-said-vessel, meansfor driving said-gagitator shafts in; oppo sitedirectionsrelative :to. the axis of the. vessel (as; viewed: from one:end thereof), to-impart op-.- positeyswirling motions :to; fluid adjacentathewespeetive' agitators so, that the, columnoffluid adjacent one:of the agitators swirls in :one direc tiontabout the axis of thelvesseland the column of; fluid: adjacent; a succeeding agitator swirls in theopposite,direction,-. the first agitator-shaft of the succession:ha-vingiat least one blade; pitched oppositely; t0v at least one:blade; of the-succeeding. agitator shaft.

6. Apparatushof the-characterdescribed:c'omprising a:tubular1 vessel,apluralityof agitator shafts arranged in axial 2 succession .-in said.-vessel and adapted to-impartopposite-swirling motions to fiuidthereadjacent, respectivelygmeans forpdrivingsaid agitator shafts sothatv the 001-, umn otfluidnadjacent one of the agitators-swirls inonedirectionabout. the axis of the vessel and the column of fluid: adjacenta succeeding agi-. tator. swirlsinthe-opposite direction, the firstagitator shaft. of: the succession having a blade pitchedoppositely toat least one blade of-the succeeding agitator shaft, and, other bladeson each saideagitator'shafts at different axial positionsrand atadifferent pitch from the. first mentioned; blade. thereon,respectively.

ARVEL O. FRANZ.

ORI-N C, KEPLINGER,

REFERENCES CITED The following references areof record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1 1,363,368 Sonstagen Dec. 28-,1940 1,961,420 Hildebrandt- June 5; 1934 2,074,988: OBrien Mar, 23, 19372,103,592 Millikan Dec; 28, 1937 2,194,666 Meissner Mar. 26;. 1940

